U.S. Frost Dates by Weather Station

NOAA station USC00396712 · South Dakota

Frost Dates for Pollock, SD

NOAA weather station Pollock (USC00396712), South Dakota · elevation 1639 ft (500 m) · hardiness zone 4a*

  • Lower-risk planting dateafter May 21only 1 spring in 10 still has a frost later
  • Typical last frostMay 850% chance of a frost after it
  • Typical first fall frostSeptember 3050% chance of a frost before it
  • Frost-free season143 daystypical year, 32°F
  • Hardiness zone4acalculated*

The year at a glance

Frost season at Pollock, SDSpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before September 30 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 143 days.JanFebMarAprMayJunJulAugSepOctNovDecLast frost ~May 8First frost ~Sep 30Frost season at Pollock, SDSpring: a frost after April 27 in 9 years out of 10, after May 8 in half of the years, after May 21 in 1 year out of 10. Fall: the first frost comes before September 18 in 1 year out of 10, before September 30 in half of the years, before October 11 in 9 years out of 10. Typical frost-free season: 143 days.JFMAMJJASONDLast frost ~May 8First frost ~Sep 30
frost likely chance fading 90% → 10% frost-free in a typical yearThe year at a glance. Blue: frost is likely; the gradient fades as the chance drops from 90% to 10%; green: the frost-free part of a typical year.

Frost dates (32°F)

Probability of frost, based on 30 years of NOAA records (1991–2020 normals)
ChanceLast frost in spring afterFirst frost in fall before
10% (unlikely)May 21September 18
50% (typical)May 8September 30
90% (likely)April 27October 11
Frost-free season (32°F, 50% chance)
143 days
Hard frost (28°F), last in spring, 50% chance after
April 30
Hard frost (28°F), first in fall, 50% chance before
October 8

The last 15 years (2006–2020 normals)

Typical last frost May 8 (same as the 30-year normal), typical first fall frost October 3 (3 days later). Frost-free season 145 days.

A shorter, more recent NOAA period. The 30-year normals above remain the main reference: 15 years carry more year-to-year noise.

Add these dates to your calendar Yearly reminders for the typical last frost, the lower-risk planting date and the typical first fall frost (.ics).

How the chance of frost changes with the date

Spring at Pollock: chance of a frost after this dateSpring, chance of a frost after the date: 10% May 21, 20% May 17, 30% May 13, 40% May 10, 50% May 8, 60% May 6, 70% May 3, 80% May 1, 90% April 27. Observed last spring frost in recent years: 2021 May 13, 2022 May 2, 2023 May 5, 2024 April 29, 2025 April 29, 2026 May 7.Spring: last frostChance of a frost after this date10%50%90%May 1Jun 1May 21May 8Apr 272021: May 132022: May 22023: May 52024: April 292025: April 292026: May 7Fall at Pollock: chance of a frost before this dateFall, chance of a frost before the date: 10% September 18, 20% September 22, 30% September 25, 40% September 27, 50% September 30, 60% October 2, 70% October 4, 80% October 7, 90% October 11. Observed first fall frost in recent years: 2021 October 23, 2022 October 7, 2023 October 7, 2024 October 8, 2025 October 22.Fall: first frostChance of a frost before this date10%50%90%Oct 1Sep 18Sep 30Oct 112021: October 232022: October 72023: October 72024: October 82025: October 22
Two charts, because spring and fall answer different questions: in spring, the chance that a frost still comes after a date; in fall, the chance that the first frost has already come before it. NOAA publishes these odds from 10% to 90%, so the lines stop there. ◆ marks the actual date in each recent year.

What actually happened in recent years

Observed dates of the last spring and first fall frost (32°F) at this station; ◆ marks them on the charts above
YearLast spring frostFirst fall frost
2021May 13October 23
2022May 2October 7
2023May 5October 7
2024April 29October 8
2025April 29October 22
2026May 7season not over yet

What these dates mean

Setting out tender crops on the early spring date of April 27 in Pollock carries a 90% chance of a light frost, making it a gamble for growers.

May 8 is the date where the probability of a light frost occurring beyond this point is 50%; September 30 is the date where the probability of a light frost having occurred by that point is 50%. The cautious date for planting tender crops in spring is May 21, while the cautious date to finish harvesting tender crops in fall is September 18.

Hard frost at 28 °F, represented by the median dates April 30 and October 8, can injure plants that survive a 32 °F light frost, so those dates are more critical for protecting crops.

How to read the probabilities

The dates are probabilities from 30 years of weather, not a forecast for this year.

  • Spring: "10% after May 21" means that in about one spring out of ten a frost still happens after that date. The 90% date is the earliest: a frost after it happens in most years.
  • Fall: "10% before September 18" means that in about one fall out of ten the first frost arrives before that date.
  • 50% is the typical date: half of the years are earlier, half are later.
  • A light frost (32°F) damages tender plants; a hard frost (28°F) also stops most hardy vegetables.

Nearby weather stations

Map of weather stations near Pollock, SDNumbered nearest stations: 1 — McLaughlin, SD — 26 mi; 2 — Selby, SD — 30 mi; 3 — Hazelton, ND — 43 mi; 4 — Ashley, ND — 45 mi; 5 — Napoleon, ND — 49 mi.ND25 mi · 40 km1. McLaughlin, SD — 26 mi12. Selby, SD — 30 mi23. Hazelton, ND — 43 mi34. Ashley, ND — 45 mi45. Napoleon, ND — 49 mi5
  1. McLaughlin, SD 26 mi (41 km)
  2. Selby, SD 30 mi (48 km)
  3. Hazelton, ND 43 mi (69 km)
  4. Ashley, ND 45 mi (72 km)
  5. Napoleon, ND 49 mi (78 km)

Sources

* Hardiness zone 4a: zone derived from PRISM 2023 grid at the station location (not the official USDA map). Source data: PRISM Group, Oregon State University.

Station coordinates: 45.9033, -100.2878.